1. Field of the Invention
The invention relates to a vehicle driving system, a control apparatus for a vehicle driving system, and a control method for a vehicle driving system and, more particularly, to changing a power transmission path of a vehicle driving system including a continuously variable transmission mechanism and a mechanical transmission mechanism in parallel with each other, the mechanical transmission mechanism having at least one gear ratio.
2. Description of Related Art
There has been suggested a vehicle driving system including a continuously variable transmission mechanism and a transmission mechanism in parallel with each other in a power transmission path between an internal combustion engine and drive wheels. The continuously variable transmission mechanism is able to continuously change a speed ratio. The transmission mechanism has at least one gear ratio. For example, a vehicle driving system described in Japanese Patent Application Publication No. 2007-278475 (JP 2007-278475 A) is one of such vehicle driving systems. In the vehicle driving system described in JP 2007-278475 A, a continuously variable transmission mechanism and a stepped transmission mechanism are provided in parallel with each other in a power transmission path between an internal combustion engine and drive wheels. When the vehicle starts moving, driving force is transmitted in a state where the stepped transmission mechanism is set to a low fixed speed step. When the vehicle speed has increased, power is transmitted by changing into the continuously variable transmission mechanism. When the vehicle speed has increased and enters a high vehicle speed region, the stepped transmission mechanism is changed into an overdrive fixed speed step, and then power is transmitted.